480MHz 10-tap clock generator using edge-combiner DLL for USB 2.0 applications

A clock generator with an edge-combiner dll (ecdll) has been developed for usb 2.0 applications. the clock generator generates 480mhz 10-tap output signals from a 12mhz reference signal and consists of three dlls to shrink the design area so that it is smaller than a conventional one based on a pll. each dll is applied to our proposed shot pulse reset technique to prevent from a harmonic lock and is applied to a voltage-controlled delay line (vcdl) with a trimming function to operate against any process voltage temperature (pvt) variations. a 90nm cmos process was used to fabricate our proposed clock generator. the 480mhz 10-tap output signals satisfy the usb 2.0 specifications. a power consumption is less than 1.3mw and a locking time is less than 3.5s,which are far less than a conventional one,10.0s. the design area is 200 225 m,which is half that of the conventional one. copyright © 2012 takashi kawamoto et al.